With the rapid development of data services, a transport network for data services has also been developed greatly. An optical transport network (OTN) is a kind of optical transport technology. The OTN includes an optical channel (OCh), an optical multiplex section (OMS), and an optical transport section (OTS). The OCh further includes three sub-layers: an optical channel payload unit-k (OPUk), an optical channel data unit-k (ODUk), and an optical channel transport unit-k (OTUk). Each sub-layer has a corresponding overhead (OH) and function to support network management and monitoring. k is an order, and represents a level, and different k values support different bit rates correspondingly. In the OTN, different protection modes may be adopted to effectively improve the survivability of services. In an existing synchronous digital hierarchy (SDH) field, a multiplex section (MS) SPRing may be realized through VC cross. However, the MS SPRing in the SDH field cannot be easily transplanted to the OTN. An OTN system has multiple ODU levels numbered 0, 1, 2, 2e, 3, 4, and so on. Problems such as how to monitor signal quality to trigger a switching, how to transfer APS information, and how to coordinate protections of a multi-level ODUk are difficult to be solved. Currently, a scheme of ODU SPRing exists in the OTN. In an implementation scheme of the existing ODU SPRing, when the system has a multi-level ODU service, a switching is performed through cross of each level of the ODUk, which may realize only protection for the current level of the ODUk, that is, the current level of the ODUk is regarded as a protection granularity. For example, the system has three levels of ODUs, which are respectively ODU2, ODU1, and ODU0, and one ODU2 may include 4 ODU1s or 8 ODU0s. A switching through cross of the ODU1 is performed to realize protection of an ODU1 level, and a switching is performed through cross of the ODU0 so as to realize protection of an ODU0 level. When multiple client services are multiplexed to the ODU2, and the multiple client services all need protection, if the protection of the ODU1 is adopted, 4 protection groups need to be created; and if the protection of the ODU0 is adopted, 8 protection groups need to be created.
The prior art has the following disadvantages: if a low order (LO) ODU is taken as a protection granularity, the number of protection groups is larger, and required switching time is long, which may even exceed a threshold of the switching time (50 ms), and consequently, the switching cannot be performed smoothly.